1. Field
Embodiments disclosed herein relate to a surgical robot used for minimally invasive surgery and a method for controlling the same.
2. Description of the Related Art
Minimally invasive surgery generally refers to surgery capable of minimizing the size of an affected area when an incision is made in the body to perform an operation. A representative example of minimally invasive surgery includes laparoscopic surgery which may involve operations in the pelvic or abdominal regions, for example. Minimally invasive surgery may involve using a surgical robot. Minimally invasive surgery may be performed while observing an image, after a plurality of small holes (incisions or invasive holes) having a size of 0.5 cm to 1.5 cm are drilled in the abdomen, and a video camera and a variety of apparatuses are inserted through the incisions. This type of surgery is unlike laparotomy in which a large incision is made in, for example, abdomen.
Minimally invasive surgery has advantages of little pain after surgery, fast recovery of intestinal motion, early food ingestion, short hospitalization period, short recovery time, and excellent cosmetic effects due to narrow incision size, as compared to laparotomy. Due to these advantages, minimally invasive surgery is used for cholecystectomy, prostatic carcinoma surgery, hernia repair and the like and applications thereof continue to grow.
A surgical robot includes a master robot to transmit a necessary signal generated by operation of a user and a slave robot to receive the signal from the master robot and directly perform operations required for surgery. The master robot and the slave robot may be integratedly or separately disposed in an operating room.
The slave robot includes a robot arm for surgical operations and surgical instruments are mounted on the front end of the robot arm. When surgery is performed using surgical instruments mounted on the front end of the robot arm, the surgical instruments move along with the movement of the robot arm.
Minimally invasive surgery using a surgical robot includes a manual positioning mode in which a user (an operator, generally a doctor or other qualified medical professional) holds and moves the robot arm on which surgical instruments are mounted such that the surgical instruments are inserted through incisions and are positioned in a surgery site, and a teleoperation mode in which a user remotely manipulates surgical instruments using a master robot. In the two modes, it is necessary to control movement of robot arms (or surgical instruments) to a limited level in order to prevent surgical instruments mounted on the robot arm from intruding into the incisions. When the limited movement of surgical instruments is not satisfied, extension of incisions or incidental bleeding of diseased parts occurs, thus causing damage to the skin or internal body parts.
Accordingly, surgical instruments mounted on the front end of the robot arm control the robot arm such that surgical instruments pivot about a virtual pivot central point set at a predetermined position. Such a virtual point is referred to as remote center of motion (RCM).
The positions of incisions are fixed via translational and rotational movement of surgical instruments and the link structure of the robot arm is designed as a parallelogrammic structure (four-link structure) in order to secure this point as the RCM. Since each link of the four-link structure necessarily passes one point regardless of movement or configuration, it is possible to realize a RCM without additional operation in both manual positioning mode and teleoperation mode.
The methods for realizing a RCM of the robot arm are broadly divided into passive type and active type. The passive type is a method in which the RCM of a robot arm is realized using a mechanical structure, while the active type is a method in which the RCM of a robot arm is realized using a control algorithm.
A method for realizing RCM using the aforementioned four-link structure by using a passive type method has a problem in that the volume of the surgical robot supporting the robot arm is increased. Also, when a surgical robot system is configured with a plurality of surgical robots, the system occupies a large area due to increased total volume, thus disadvantageously causing a narrow workspace, and there is further an increased risk of collision between surgical robots during a surgical operation.